1. Field of the Invention
The present invention relates to an information record medium for automatically determining a record power with respect to the information record medium such as an optical disc, and recording the information thereon.
2. Description of the Related Art
There is a write once (WO: Write Once) type optical disc, in which information can be written to the same location only once by using a condition change of organic pigment, as an optical record medium capable of postscript-writing.
For example, triphenyl-methane type pigment, fluoran type pigment, cyanine type pigment or the like is used as a record material, in the write once type optical disc using the organic pigment for the record film. By using those record materials, a pit is formed by the rear flow mechanism in which a vapor pressure in the vicinity of the surface of a record portion made from the record material is increased by the radiation of a light beam and the like, and this vapor pressure causes a fused portion to be peripherally expanded, which can correspond to "1" or "0" of digital data.
By the way, in the optical disc using the organic type pigment, a temperature at which the above-mentioned rear flow is induced is different depending on the record material. Thus, a power (electric power) of the light beam irradiated to form the pit is different for each kind of optical disc.
Therefore, in order to record the information onto the optical disc using the organic type pigment, a laser power optimal for the optical disc of each kind is encoded and recorded on a part of the optical disc, for example, a control track or a lead in area.
However, even if the same record material is used, the performance may be slightly different for each individual disc, in many cases. For this reason, the optimal laser power may not be irradiated onto the individual optical disc, if the laser power is uniformly applied for each kind of the optical disc.
That is, if the laser power is uniformly applied to the same type of optical disc as in the conventional technique, the influence resulting from the change of ambient environment, the change of record/reproduction performance for each optical disc or the like leads to a trouble that the information cannot be stably recorded.
So, a calibration of the laser power may be carried out prior to the actual start of the recording operation. In this calibration, a test signal is recorded on a test record region, which is prepared on the optical disc, by gradually changing the laser power, and the recorded test signal is reproduced. Then, the information is actually recorded at a record power which is obtained by the calibration to be optimal for the combination of a recorder and a record medium.
However, the record medium may have a defect caused by crack, dust and the like. The existence of such a defect on a location to which the test signal is written results in a problem that the signal quality of a record signal (i.e. the test signal) cannot be checked correctly.
In short, even if the test signal is recorded at the record power which is supposed to be optimal, when the defect is present on the recorded location, the reproduction signal for the test signal is not admitted to be the optimal signal. Thus, the record power used to record this test signal is not set as the optimal record power. On the contrary, although the test signal is not recorded at the optimal record power, the defect may cause the reproduction signal for this test signal to be admitted to be the optimal signal, and also cause a non-optimal record power to be erroneously set as the optimal record power. As a result, even if such a calibration has been performed, there may be a case where the information is not actually recorded at the record power optimal for the combination of the recorder and the record medium.
On the other hand, the recording operation with the optimal record power may not be performed not only in a case that the defect is present at the record position but also in a case that an abnormal condition in the servo system e.g., an external disturbance is generated at the time of recording.